Definition: A sheet of saline water separated from the open sea by sand or shingle banks. The sheet of water between an offshore reef, especially of coral and mainland. The sheet of water within a ring or horseshoe shaped atoll.
Comment: "Small" is ambiguous. For details on "Small lakes" (e.g. Cameroon crater lakes) see http://worldwildlife.org/biomes/small-lake-ecosystems. This class will be replaced with a less ambiguous class.